散列内容访问与不同的Perl版本不一致

Question

[在perl 5.22.1和perl 5.30.0中使用以下代码遇到了一个有趣的问题

use strict;
use warnings;
use feature 'say';

#use Data::Dumper;

my %hash;
my %seen;
my @header = split ',', <DATA>;

chomp @header;

while(<DATA>) {
    next if /^\s*$/;
    chomp;
    my %data;
    @data{@header} = split ',';

    push @{$hash{person}}, \%data;
    push @{$hash{Position}{$data{Position}}}, "$data{First} $data{Last}";
    if( ! $seen{$data{Position}} ) {
        $seen{$data{Position}} = 1;
        push @{$hash{Role}}, $data{Position};
    }
}

#say Dumper($hash{Position});

my $count = 0;
for my $person ( @{$hash{person}} ) {
    say "Person: $count";
    say "Role: $person->{Position}";
}

say "---- Groups ----\n";

while( my($p,$m) = each %{$hash{Position}} ) {
    say "-> $p";
    my $members = join(',',@{$m});
    say "-> Members: $members\n";
}

say "---- Roles ----";

say '-> ' . join(', ',@{$hash{Role}});

__DATA__
First,Last,Position
John,Doe,Developer
Mary,Fox,Manager
Anna,Gulaby,Developer

如果代码按原样运行-everything works fine

现在将$count++增量添加为波纹管和code produces errors就足够了>

my $count = 0;
for my $person ( @{$hash{person}} ) {
    $count++;
    say "Person: $count";
    say "Role: $person->{Position}";
}
错误：

Error(s), warning(s):
Use of uninitialized value $data{"Position"} in hash element at source_file.pl line 22, <DATA> line 2.
Use of uninitialized value $data{"Position"} in hash element at source_file.pl line 23, <DATA> line 2.
Use of uninitialized value $data{"Position"} in hash element at source_file.pl line 24, <DATA> line 2.
Use of uninitialized value $data{"Position"} in hash element at source_file.pl line 22, <DATA> line 3.
Use of uninitialized value $data{"Position"} in hash element at source_file.pl line 23, <DATA> line 3.
Use of uninitialized value $data{"Position"} in hash element at source_file.pl line 22, <DATA> line 4.
Use of uninitialized value $data{"Position"} in hash element at source_file.pl line 23, <DATA> line 4.
Use of uninitialized value in concatenation (.) or string at source_file.pl line 35, <DATA> line 4.
Use of uninitialized value in concatenation (.) or string at source_file.pl line 35, <DATA> line 4.
Use of uninitialized value in concatenation (.) or string at source_file.pl line 35, <DATA> line 4.
Use of uninitialized value in join or string at source_file.pl line 48, <DATA> line 4.
此问题不会在perl 5.30.0（Windows 10，Strawberry Perl）或Perl v5.24.2中显现出来。

注意：

问题不仅通过$count++显现出来，而且以其他任何方式访问say "Person: $count";-post# 60653651]之后的哈希值也显示出来。

我想听听对此情况的评论，原因是什么？

我遇到了一个有趣的问题，在perl 5.22.1和perl 5.30.0中使用以下代码使用strict;使用警告；使用功能“说”； #use Data :: Dumper;我的％hash;我的％seen;我的@header = ...

Answer 1

我可以通过（在Linux上）首先将源文件转换为Windows样式的\r\n行尾，然后尝试运行它来复制此行为。因此，我怀疑在测试各种版本时，有时会使用Windows，而在其他时候则使用Linux / Unix，并且没有正确转换文件的行尾。

@chomp仅删除换行符（Well，$/的当前值是多余的），因此，在以Windows样式行结尾的字符串上使用时，它将保留回车符。哈希键不是"Position"，而是"Position\r"，这不是其余代码使用的键。